An engine's air-fuel ratio may be controlled to reduce engine emissions. During some conditions, the engine's air-fuel ratio may deviate from a desired air-fuel ratio due to manufacturing variation or degradation of engine components. One source of engine air-fuel ratio error may be fuel injectors not delivering a desired or expected amount of fuel. Another source of engine air-fuel error may be an inaccurate engine air flow estimate based on an engine air flow sensor. An aggregate air-fuel ratio error may be determined via an oxygen sensor position in the engine's exhaust system, but the aggregate error provides little insight into whether the air-fuel error is a result of fueling or the engine air flow estimate. The engine air-fuel ratio error may be corrected via injecting more or less fuel to the engine. However, if the engine air-fuel error was actually a result of an engine air flow estimate, adjustments to engine air flow related actuators and determination of engine air flow related control parameters, such as engine torque, may be improper. Therefore, it may be desirable to provide separate and accurate estimates of engine air flow and fuel flow.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method, comprising: receiving vehicle information from one or more sensors to a controller; adjusting a value of a first transfer function responsive to motor/generator operating conditions and an output of a second transfer function, the first transfer function a first basis for determining engine air flow, the second transfer function a second basis for determining engine air flow; and adjusting a torque actuator of an engine responsive to the adjusted value.
By updating a first engine air flow related transfer function responsive to motor/generator conditions and a second engine air flow related transfer function, it may be possible to improve engine air flow estimates without having to rely on estimated exhaust gas concentrations. Further, by not using an oxygen sensor to estimate engine air flow it may be possible to reduce a number of variables that may influence engine air flow determination. For example, it may be possible to estimate engine air flow when an engine is rotating but not combusting air and fuel. Consequently, parameters that may influence air flow through the engine, such as fuel properties and spark timing, may be eliminated from engine air flow estimates so that engine air flow variability may be reduced.
The present description may provide several advantages. Specifically, the approach may improve vehicle efficiency over a vehicle's life cycle. Further, the approach may reduce engine air-fuel mixture variation. Further still, the approach may improve engine torque control by improving engine torque estimates.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.